Imaging apparatus have been widely used for diagnosis of arteriosclerosis, for diagnosis before operation at the time of an endovascular treatment by a high functional catheter such as a balloon catheter, a stent and the like, or for confirming the result after an operation.
An example of an imaging apparatus for diagnosis is an intravascular ultrasound (IVUS) apparatus. Generally, the intravascular ultrasound apparatus radial-operates an ultrasonic probe unit installed with a transmitting and receiving unit composed of an ultrasound transducer inside a blood vessel, a reflected wave (ultrasonic echo) reflected by a biological tissue inside a body cavity of a test subject is received by the transmitting and receiving unit and thereafter, based on the intensity of an ultrasonic echo signal generated by applying a process of amplification, detection or the like, a cross-sectional image of the blood vessel is to be visualized.
Also, another known imaging apparatus is an optical coherent tomography (OCT) apparatus which carries out diagnostic imaging by utilizing coherence of light.
The optical coherent tomography apparatus is an apparatus in which a measurement light is emitted inside a blood vessel while rotating a transmitting and receiving unit while inserting an optical probe unit which is built-in with the transmitting and receiving unit mounted with an optical lens and an optical mirror at the distal end and an optical fiber inside the blood vessel, a radial scan is carried out with receiving reflected light from a biological tissue, and a cross-sectional image of the blood vessel is visualized based on interference signal obtained by making the reflected light obtained depending on this radial scan and a reference light split from the measurement light beforehand interfere each other.
Further, recently, as an enhancement of the optical coherent tomography apparatus, there has been developed an optical frequency domain imaging (OFDI) apparatus which utilizes wavelength sweep.
With respect to the optical frequency domain imaging apparatus utilizing wavelength sweep, the basic constitution is similar as that of the optical coherent tomography apparatus, but a light source having a longer wavelength compared with the optical coherent tomography apparatus is used and also, light having different wavelengths is emitted continuously. Then, mechanism for variably changing the optical path length of the reference light is made unnecessary by employing a constitution in which reflected-light intensity at each point in the depth direction of the biological tissue is found out by frequency analysis of interference signal.
In the description hereinafter, the intravascular ultrasound (IVUS) apparatus, the optical coherent tomography (OCT) apparatus and the optical frequency domain imaging (OFDI) apparatus utilizing wavelength sweep are named generically and referred to as an “imaging apparatus”.
Generally, when visualizing a cross-sectional image by using those imaging apparatuses, an X-ray image processing apparatus is used together concurrently. This is because it is effective for making a decision about the treatment region or the like while seeing an angiographic image generated in the X-ray image processing apparatus, and for confirming the contrast marker which the ultrasonic probe unit or the optical probe unit possesses based on the angiographic image and comprehending the position of the ultrasonic probe unit or the optical probe unit. Consequently, it is desirable for the angiographic image (X-ray image) generated in the X-ray image processing apparatus and the cross-sectional image visualized by using the imaging apparatus to be stored and displayed by being mutually correlated with each other.
With this back ground, for example, Japanese Patent No. 3167367 proposes a method in which an angiographic image generated in an X-ray image processing apparatus and a cross-sectional image visualized in an intravascular ultrasound apparatus are held and displayed by being mutually correlated with each other.